The incidence of dermatoses and allergy to metals (Cr, Co, Ni) was determined in 1782 workers exposed to cement, waste fly ash and asbestos cement. They were also exposed to reclaimed (used), mineral oils. Dermatitis was found in 23.6% of the subjects, and oil acne in 11.2%. Allergy to chromium was found in 23% of the subjects; the % of definitely positive patch test results (the total of positive +(+) and strongly positive +(+)+ was, however, 8.6%. Allergy to cobalt was found in 13.4% of the subjects examined (definite in 3.1%). Allergy to nickel was found in 2.7% of the subjects (definite in 1.1%). The risks of occurrence of occupational skin disease and allergy to metals in subjects exposed to ash were found to be lower than in subjects exposed to cement, and were similar to those in subjects exposed to asbestos cement. Overall chromium, cobalt and nickel contents in ash and asbestos were higher than in cement. Soluble chromium compound content in ash was lower than in cement from European countries and similar to that in American cement.